Yabe, H. & Obata, T. (1930)
On some fossil fishes from the Cretaceous of Japan. Japanese Journal of Geology and Geography, 3, 1–7

Yabe, H. & Obata, T. (1930)
Discovery of Ptychodus rugosus Dixon from the Upper Cretaceous of the Japanes Saghalin. Japanese Journal of Geology and Geography, 7(2), 43–44